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Reland "[libc][math][c23] Implement C23 math function asinpif16" (#152690)

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#146226 with fixing asinpi MPFR number function and make it work when
mpfr < `4.2.0`
This commit is contained in:
Mohamed Emad 2025-08-18 00:04:47 +03:00 committed by GitHub
parent 5892a2beec
commit 40833eea21
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
16 changed files with 347 additions and 1 deletions
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1
libc/config/linux/aarch64/entrypoints.txt
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@ -660,6 +660,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
list(APPEND TARGET_LIBM_ENTRYPOINTS
# math.h C23 _Float16 entrypoints
# libc.src.math.acoshf16
libc.src.math.asinpif16
libc.src.math.canonicalizef16
libc.src.math.ceilf16
libc.src.math.copysignf16

1
libc/config/linux/x86_64/entrypoints.txt
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@ -704,6 +704,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
libc.src.math.acospif16
libc.src.math.asinf16
libc.src.math.asinhf16
libc.src.math.asinpif16
libc.src.math.atanf16
libc.src.math.atanhf16
libc.src.math.canonicalizef16

2
libc/docs/headers/math/index.rst
View File

@ -268,7 +268,7 @@ Higher Math Functions
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
| asinh | |check| | | | |check| | | 7.12.5.2 | F.10.2.2 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
| asinpi | | | | | | 7.12.4.9 | F.10.1.9 |
| asinpi | | | | |check| | | 7.12.4.9 | F.10.1.9 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
| atan | |check| | 1 ULP | | |check| | | 7.12.4.3 | F.10.1.3 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+

7
libc/include/math.yaml
View File

@ -79,6 +79,13 @@ functions:
arguments:
- type: _Float16
guard: LIBC_TYPES_HAS_FLOAT16
- name: asinpif16
standards:
- stdc
return_type: _Float16
arguments:
- type: _Float16
guard: LIBC_TYPES_HAS_FLOAT16
- name: atan
standards:
- stdc

2
libc/src/math/CMakeLists.txt
View File

@ -58,6 +58,8 @@ add_math_entrypoint_object(asinh)
add_math_entrypoint_object(asinhf)
add_math_entrypoint_object(asinhf16)
add_math_entrypoint_object(asinpif16)
add_math_entrypoint_object(atan)
add_math_entrypoint_object(atanf)
add_math_entrypoint_object(atanf16)

21
libc/src/math/asinpif16.h Normal file
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@ -0,0 +1,21 @@
//===-- Implementation header for asinpif16 ---------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIBC_SRC_MATH_ASINPIF16_H
#define LLVM_LIBC_SRC_MATH_ASINPIF16_H
#include "src/__support/macros/config.h"
#include "src/__support/macros/properties/types.h"
namespace LIBC_NAMESPACE_DECL {
float16 asinpif16(float16 x);
} // namespace LIBC_NAMESPACE_DECL
#endif // LLVM_LIBC_SRC_MATH_ASINPIF16_H

19
libc/src/math/generic/CMakeLists.txt
View File

@ -4035,6 +4035,25 @@ add_entrypoint_object(
libc.src.__support.math.asinhf16
)
add_entrypoint_object(
asinpif16
SRCS
asinpif16.cpp
HDRS
../asinpif16.h
DEPENDS
libc.hdr.errno_macros
libc.hdr.fenv_macros
libc.src.__support.FPUtil.cast
libc.src.__support.FPUtil.except_value_utils
libc.src.__support.FPUtil.fenv_impl
libc.src.__support.FPUtil.fp_bits
libc.src.__support.FPUtil.multiply_add
libc.src.__support.FPUtil.polyeval
libc.src.__support.FPUtil.sqrt
libc.src.__support.macros.optimization
)
add_entrypoint_object(
atanhf
SRCS

127
libc/src/math/generic/asinpif16.cpp Normal file
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@ -0,0 +1,127 @@
//===-- Half-precision asinpif16(x) function ------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception.
//
//===----------------------------------------------------------------------===//
#include "src/math/asinpif16.h"
#include "hdr/errno_macros.h"
#include "hdr/fenv_macros.h"
#include "src/__support/FPUtil/FEnvImpl.h"
#include "src/__support/FPUtil/FPBits.h"
#include "src/__support/FPUtil/PolyEval.h"
#include "src/__support/FPUtil/cast.h"
#include "src/__support/FPUtil/except_value_utils.h"
#include "src/__support/FPUtil/multiply_add.h"
#include "src/__support/FPUtil/sqrt.h"
#include "src/__support/macros/optimization.h"
namespace LIBC_NAMESPACE_DECL {
LLVM_LIBC_FUNCTION(float16, asinpif16, (float16 x)) {
using FPBits = fputil::FPBits<float16>;
FPBits xbits(x);
bool is_neg = xbits.is_neg();
double x_abs = fputil::cast<double>(xbits.abs().get_val());
auto signed_result = [is_neg](auto r) -> auto { return is_neg ? -r : r; };
if (LIBC_UNLIKELY(x_abs > 1.0)) {
// aspinf16(NaN) = NaN
if (xbits.is_nan()) {
if (xbits.is_signaling_nan()) {
fputil::raise_except_if_required(FE_INVALID);
return FPBits::quiet_nan().get_val();
}
return x;
}
// 1 < |x| <= +/-inf
fputil::raise_except_if_required(FE_INVALID);
fputil::set_errno_if_required(EDOM);
return FPBits::quiet_nan().get_val();
}
// the coefficients for the polynomial approximation of asin(x)/pi in the
// range [0, 0.5] extracted using python-sympy
//
// Python code to generate the coefficients:
// > from sympy import *
// > import math
// > x = symbols('x')
// > print(series(asin(x)/math.pi, x, 0, 21))
//
// OUTPUT:
//
// 0.318309886183791*x + 0.0530516476972984*x**3 + 0.0238732414637843*x**5 +
// 0.0142102627760621*x**7 + 0.00967087327815336*x**9 +
// 0.00712127941391293*x**11 + 0.00552355646848375*x**13 +
// 0.00444514782463692*x**15 + 0.00367705242846804*x**17 +
// 0.00310721681820837*x**19 + O(x**21)
//
// it's very accurate in the range [0, 0.5] and has a maximum error of
// 0.0000000000000001 in the range [0, 0.5].
constexpr double POLY_COEFFS[] = {
0x1.45f306dc9c889p-2, // x^1
0x1.b2995e7b7b5fdp-5, // x^3
0x1.8723a1d588a36p-6, // x^5
0x1.d1a452f20430dp-7, // x^7
0x1.3ce52a3a09f61p-7, // x^9
0x1.d2b33e303d375p-8, // x^11
0x1.69fde663c674fp-8, // x^13
0x1.235134885f19bp-8, // x^15
};
// polynomial evaluation using horner's method
// work only for |x| in [0, 0.5]
auto asinpi_polyeval = [](double x) -> double {
return x * fputil::polyeval(x * x, POLY_COEFFS[0], POLY_COEFFS[1],
POLY_COEFFS[2], POLY_COEFFS[3], POLY_COEFFS[4],
POLY_COEFFS[5], POLY_COEFFS[6], POLY_COEFFS[7]);
};
// if |x| <= 0.5:
if (LIBC_UNLIKELY(x_abs <= 0.5)) {
// Use polynomial approximation of asin(x)/pi in the range [0, 0.5]
double result = asinpi_polyeval(fputil::cast<double>(x));
return fputil::cast<float16>(result);
}
// If |x| > 0.5, we need to use the range reduction method:
// y = asin(x) => x = sin(y)
// because: sin(a) = cos(pi/2 - a)
// therefore:
// x = cos(pi/2 - y)
// let z = pi/2 - y,
// x = cos(z)
// because: cos(2a) = 1 - 2 * sin^2(a), z = 2a, a = z/2
// therefore:
// cos(z) = 1 - 2 * sin^2(z/2)
// sin(z/2) = sqrt((1 - cos(z))/2)
// sin(z/2) = sqrt((1 - x)/2)
// let u = (1 - x)/2
// then:
// sin(z/2) = sqrt(u)
// z/2 = asin(sqrt(u))
// z = 2 * asin(sqrt(u))
// pi/2 - y = 2 * asin(sqrt(u))
// y = pi/2 - 2 * asin(sqrt(u))
// y/pi = 1/2 - 2 * asin(sqrt(u))/pi
//
// Finally, we can write:
// asinpi(x) = 1/2 - 2 * asinpi(sqrt(u))
// where u = (1 - x) /2
// = 0.5 - 0.5 * x
// = multiply_add(-0.5, x, 0.5)
double u = fputil::multiply_add(-0.5, x_abs, 0.5);
double asinpi_sqrt_u = asinpi_polyeval(fputil::sqrt<double>(u));
double result = fputil::multiply_add(-2.0, asinpi_sqrt_u, 0.5);
return fputil::cast<float16>(signed_result(result));
}
} // namespace LIBC_NAMESPACE_DECL

11
libc/test/src/math/CMakeLists.txt
View File

@ -2282,6 +2282,17 @@ add_fp_unittest(
libc.src.math.asinf16
)
add_fp_unittest(
asinpif16_test
NEED_MPFR
SUITE
libc-math-unittests
SRCS
asinpif16_test.cpp
DEPENDS
libc.src.math.asinpif16
)
add_fp_unittest(
acosf_test
NEED_MPFR

40
libc/test/src/math/asinpif16_test.cpp Normal file
View File

@ -0,0 +1,40 @@
//===-- Exhaustive test for asinpif16 -------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "src/math/asinpif16.h"
#include "test/UnitTest/FPMatcher.h"
#include "test/UnitTest/Test.h"
#include "utils/MPFRWrapper/MPFRUtils.h"
using LlvmLibcAsinpif16Test = LIBC_NAMESPACE::testing::FPTest<float16>;
namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
// Range: [0, Inf]
static constexpr uint16_t POS_START = 0x0000U;
static constexpr uint16_t POS_STOP = 0x7c00U;
// Range: [-Inf, 0]
static constexpr uint16_t NEG_START = 0x8000U;
static constexpr uint16_t NEG_STOP = 0xfc00U;
TEST_F(LlvmLibcAsinpif16Test, PositiveRange) {
for (uint16_t v = POS_START; v <= POS_STOP; ++v) {
float16 x = FPBits(v).get_val();
EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Asinpi, x,
LIBC_NAMESPACE::asinpif16(x), 0.5);
}
}
TEST_F(LlvmLibcAsinpif16Test, NegativeRange) {
for (uint16_t v = NEG_START; v <= NEG_STOP; ++v) {
float16 x = FPBits(v).get_val();
EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Asinpi, x,
LIBC_NAMESPACE::asinpif16(x), 0.5);
}
}

12
libc/test/src/math/smoke/CMakeLists.txt
View File

@ -4216,6 +4216,18 @@ add_fp_unittest(
libc.src.math.asinhf16
)
add_fp_unittest(
asinpif16_test
NEED_MPFR
SUITE
libc-math-unittests
SRCS
asinpif16_test.cpp
DEPENDS
libc.src.math.asinpif16
libc.src.errno.errno
)
add_fp_unittest(
acoshf_test
SUITE

86
libc/test/src/math/smoke/asinpif16_test.cpp Normal file
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@ -0,0 +1,86 @@
//===-- Unittests for asinpif16 -------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "src/__support/libc_errno.h"
#include "src/math/asinpif16.h"
#include "test/UnitTest/FPMatcher.h"
using LlvmLibcAsinpif16Test = LIBC_NAMESPACE::testing::FPTest<float16>;
TEST_F(LlvmLibcAsinpif16Test, SpecialNumbers) {
// zero
EXPECT_FP_EQ(zero, LIBC_NAMESPACE::asinpif16(zero));
// +/-1
EXPECT_FP_EQ(0.5f16, LIBC_NAMESPACE::asinpif16(1.0));
EXPECT_FP_EQ(-0.5f16, LIBC_NAMESPACE::asinpif16(-1.0));
// NaN inputs
EXPECT_FP_EQ(FPBits::quiet_nan().get_val(),
LIBC_NAMESPACE::asinpif16(FPBits::quiet_nan().get_val()));
EXPECT_FP_EQ(FPBits::quiet_nan().get_val(),
LIBC_NAMESPACE::asinpif16(FPBits::signaling_nan().get_val()));
// infinity inputs -> should return NaN
libc_errno = 0;
EXPECT_FP_EQ(FPBits::quiet_nan().get_val(), LIBC_NAMESPACE::asinpif16(inf));
EXPECT_MATH_ERRNO(EDOM);
libc_errno = 0;
EXPECT_FP_EQ(FPBits::quiet_nan().get_val(),
LIBC_NAMESPACE::asinpif16(neg_inf));
EXPECT_MATH_ERRNO(EDOM);
}
TEST_F(LlvmLibcAsinpif16Test, OutOfRange) {
// Test values > 1
libc_errno = 0;
EXPECT_FP_EQ(FPBits::quiet_nan().get_val(),
LIBC_NAMESPACE::asinpif16(1.5f16));
EXPECT_MATH_ERRNO(EDOM);
libc_errno = 0;
EXPECT_FP_EQ(FPBits::quiet_nan().get_val(),
LIBC_NAMESPACE::asinpif16(2.0f16));
EXPECT_MATH_ERRNO(EDOM);
// Test values < -1
libc_errno = 0;
EXPECT_FP_EQ(FPBits::quiet_nan().get_val(),
LIBC_NAMESPACE::asinpif16(-1.5f16));
EXPECT_MATH_ERRNO(EDOM);
libc_errno = 0;
EXPECT_FP_EQ(FPBits::quiet_nan().get_val(),
LIBC_NAMESPACE::asinpif16(-2.0f16));
EXPECT_MATH_ERRNO(EDOM);
// Test maximum normal value (should be > 1 for float16)
libc_errno = 0;
EXPECT_FP_EQ(FPBits::quiet_nan().get_val(),
LIBC_NAMESPACE::asinpif16(FPBits::max_normal().get_val()));
EXPECT_MATH_ERRNO(EDOM);
}
TEST_F(LlvmLibcAsinpif16Test, SymmetryProperty) {
// Test that asinpi(-x) = -asinpi(x)
constexpr float16 TEST_VALS[] = {0.1f16, 0.25f16, 0.5f16, 0.75f16,
0.9f16, 0.99f16, 1.0f16};
for (float16 x : TEST_VALS) {
FPBits neg_x_bits(x);
neg_x_bits.set_sign(Sign::NEG);
float16 neg_x = neg_x_bits.get_val();
float16 pos_result = LIBC_NAMESPACE::asinpif16(x);
float16 neg_result = LIBC_NAMESPACE::asinpif16(neg_x);
EXPECT_FP_EQ(pos_result, FPBits(neg_result).abs().get_val());
}
}

15
libc/utils/MPFRWrapper/MPCommon.cpp
View File

@ -105,6 +105,21 @@ MPFRNumber MPFRNumber::asinh() const {
return result;
}
MPFRNumber MPFRNumber::asinpi() const {
MPFRNumber result(*this);
#if MPFR_VERSION >= MPFR_VERSION_NUM(4, 2, 0)
mpfr_asinpi(result.value, value, mpfr_rounding);
return result;
#else
MPFRNumber value_asin(0.0, 1280);
mpfr_asin(value_asin.value, value, MPFR_RNDN);
MPFRNumber value_pi(0.0, 1280);
mpfr_const_pi(value_pi.value, MPFR_RNDN);
mpfr_div(result.value, value_asin.value, value_pi.value, mpfr_rounding);
return result;
#endif
}
MPFRNumber MPFRNumber::atan() const {
MPFRNumber result(*this);
mpfr_atan(result.value, value, mpfr_rounding);

1
libc/utils/MPFRWrapper/MPCommon.h
View File

@ -189,6 +189,7 @@ public:
MPFRNumber add(const MPFRNumber &b) const;
MPFRNumber asin() const;
MPFRNumber asinh() const;
MPFRNumber asinpi() const;
MPFRNumber atan() const;
MPFRNumber atan2(const MPFRNumber &b);
MPFRNumber atanh() const;

2
libc/utils/MPFRWrapper/MPFRUtils.cpp
View File

@ -39,6 +39,8 @@ unary_operation(Operation op, InputType input, unsigned int precision,
return mpfrInput.asin();
case Operation::Asinh:
return mpfrInput.asinh();
case Operation::Asinpi:
return mpfrInput.asinpi();
case Operation::Atan:
return mpfrInput.atan();
case Operation::Atanh:

1
libc/utils/MPFRWrapper/MPFRUtils.h
View File

@ -30,6 +30,7 @@ enum class Operation : int {
Acospi,
Asin,
Asinh,
Asinpi,
Atan,
Atanh,
Cbrt,